为什么::first-letter中的文本装饰不能在::first-line中级联文本装饰？

看来，text-decoration在::first-letter不能级联text-decoration中::first-line。这是代码：

p::first-line {
  color: orange;
  font-size: 22px;
  text-decoration: line-through;
}

p::first-letter {
  color: green;
  font-size: 36px;
  text-transform: capitalize;
  text-decoration: none !important;
}

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